A time-to-digital converter is mainly applied in an all digital phase locked loop circuit, and a function of the time-to-digital converter is to measure a phase difference between two clock signals and convert the phase difference into a digital signal. As shown in FIG. 1, a time-to-digital converter includes a delay circuit 101 and a determining circuit 102. The delay circuit 101 is configured to input two clock signals, which are an external reference clock signal FREF and a feedback clock signal CKV, delay the two clock signals, and after being triggered by a trigger in the determining circuit 102, obtain a quantized time interval between the two clock signals. The delay circuit 101 may consist of cursor delay links, and the cursor delay links include a first delay link and a second delay link. A time for which a delay may last when the FREF passes through a delay unit in the first delay link is τ1, and a time for which a delay may last when the CKV passes through a delay unit in the second delay link is τ2, where τ1>τ2. When the FREF is transmitted in the first delay link and the CKV is transmitted in the second delay link, each time the two clock signals pass through one delay unit, a time difference between the two clock signals increases by TR, where TR=(τ1−τ2), and the time difference TR is time accuracy. Assuming that an output sequence Q changes from 1 to 0 after the clock signals pass through N stages of delay units, where N is an integer greater than 0, and the sequence Q=[Q1, Q2, Q3, . . . , QL], it indicates that a measurement time difference between rising edges of the two signals is N·TR. ThFREFore, when the time accuracy is determined, a greater measurement time difference between the FREF signal and the CKV signal indicates a greater N, that is, more delay units are needed. As a result, a problem existing in the prior art is that: when the measurement time difference between the FREF signal and the CKV signal is great, more delay units are needed to ensure certain time accuracy, thereby increasing a circuit scale.